Get 11 HP More From Your Hemi With This Easy Bolt-On!

Have you ever been within earshot of a group of gearheads on a test & tune night at the drag strip as they casually peek under an open hood to study the basically stock late-model mill? One of them pipes up: “Those aftermarket coils won’t do a thing except waste money.” Another quickly speaks up in their defense: “More spark equals more power.” We think this bench-racing scenario plays out due to a major lack of real test data versus “message board” anecdotes. The fact that the late-model Gen III Hemi has 16 spark plugs, all mounted on the valve cover within easy reach, makes a coil pack swap an ideal candidate for an easy weekend DIY project. With so many companies offering them in a variety of designer colors, we wondered which camp was right. Is adding aftermarket coils on a late-model Hemi a waste of money? Or would it add enough power to move the dyno needle and make the spend worth it?

We had an all-stock 5.7L Hemi (with a 93-octane tune) in a 2006 Charger that was the ideal candidate to attempt to answer these questions. The Hemi employs eight coil-on-plug (COP) coils, so any performance changes would be a direct result of the coils and the plugs. We contacted Steve Davis, President of Performance Distributors in Memphis, to see what he had for our Charger. Davis suggested the Sultans of Spark (SOS) COP coils for the Hemi (part no. 45850 for ’06-’12 Chargers) which cost $379 for the set.

Upon receiving the SOS coils, it was hard to tell the difference between them and the OE coils, and wondered if they could provide a greater output. We did, however, appreciate the stock look, as fashionista colors often look out of place and draw unwanted attention. Davis assured us that looks can be deceiving. Just like the OE coils, the SOS coils are induction coils, but the similarity end there. The SOS coils have heavier gauge windings, and there are more of them within each coil. The SOS coils provide up to 40,000 volts under load (hard acceleration) while the OEM coils produce only 25,000 volts. That’s a voltage potential increase of 38 percent by doing nothing more than swapping to the SOS coils.

With the SOS coils, a wider-than-stock plug gap of .065 inch is suggested. The theory is a wider gap allows a more complete burn of the air/fuel mixture resulting in more power. An OEM coil may miss under hard acceleration with such a wide gap, but the SOS coils with the 15,000 volts in reserve do not suffer the same saturation roll-off (voltage loss) as OEM coils. As we later discovered, even with the increased voltage, the SOS coils do not operate any warmer than the OEM coils, and the use of high-grade epoxy helps improve the durability of the coils. To accompany the SOS coils, sixteen Autolite platinum plugs were dropped in (part no. 5263, $1.52 each). Davis recommended the Autolites because they are more resistant to tip erosion with the wider gaps.

Before we did any coil swapping, we dropped by Pennsylvania College of Technology in Williamsport, PA, to use their Mustang chassis dyno and establish our baseline performance. We strapped down the Charger on to the dyno and planted the throttle to the floor on three successive runs from 3,500 to 5,500 rpm. The baseline torque peak was 337 lb-ft of torque at 4,300 rpm and a peak of 303 hp at 5,250 rpm.

After the completion of the baseline runs, the electrical pigtail on each coil was disconnected and the two fasteners on each coil were loosened, freeing the coils from the valve cover. The old coils were set aside, and the Performance distributor coils were put on top of the old Champion plugs with the factory .040-inch gap. Since so many people replace the plugs and the coils at the same time, we wanted to eliminate any change being the result of a plug swap or gap change. With that set-up, the Hemi Charger spun the dyno wheels to 313.2 peak hp (at 5,150 rpm) and 345 peak lb-ft of torque (coming at 4,200 rpm). We were up 10.2 hp and 8 lb-ft over the baseline—that’s a difference most calibrated butts can feel.

Next, we gapped our new Autolites to .065 inch, torqued them in, and put the SOS coils back on. The idea was to see what kind of gain most people would see all-in, with new coils, new plugs, and bigger gaps. With the new coils and plugs, the Charger was again run on the dyno for three runs. The SOS coils and new Champion plugs pushed the peak torque up to 347 lb-ft at 4,250 rpm, and the horsepower jumped to 314 hp at 5,150 rpm. The peak numbers were up another 1 hp and 2 lb-ft from just the coil packs alone.

Based upon our testing, the SOS coils were a success. The increased voltage provided a broad torque curve in the lower rpm that greatly surpassed the OE coils. The Hemi sounded great, performed well, and had no drivability concerns. While not all results will match ours, the chassis dyno testing of aftermarket coils seems to prove that, at least where the Performance Distributors SOS coils are concerned, a coil pack upgrade is worth the money.

The subject of our test: Performance Distributors has developed the Sultans of Spark (SOS) coil-on-plug coil (COP) for the late-model Gen III Hemi Charger (’06-’12, part no. 45850, $379 for the set of eight). Will it add performance to our Hemi?To match the SOS coils, Performance distributors recommends Autolite platinum plugs. Sixteen Autolite plugs (part no. 5236, $1.52 each) were properly gapped to the recommended .065-inch spark gap. “We’ve found over the years that the Autolite platinum plugs are very good about maintaining the wider gaps over time,” stated Steve Davis of Performance distributors.The test vehicle for the SOS coils is a former police car belonging to the author. The 2006 Charger is equipped with a factory replacement 340-horse 5.7L Hemi with 31K miles and an even newer factory replacement NAG 1 transmission with only 19K miles on it.A baseline series of runs was established. We paid a visit to Pennsylvania College of Technology in Williamsport, PA to use their Mustang chassis dyno to perform the SOS coil testing. We established a baseline of three runs, then dyno’ed just the coils, then added the plugs with the SOS coils.Our stock 5.7L Hemi was subjected to a 3,500 to 5,500 rpm test range, and has a 93-octane tune installed prior to the baseline testing. The average of the three baseline runs revealed a peak of 337 lb-ft for torque (at 4,300 rpm) and 303 for hp (at 5,250 rpm). The average of the runs over the 2,000rpm sweep was 316 lb-ft of torque and 277 hp.With the baseline established, it was time to dive into the engine bay and swap parts. The removal of the coils was relatively straightforward. The electrical connector must be disconnected, and the coil pack loosened with a 10mm socket. Once free of the valve covers, they pull right out.The SOS coil (left) is next to the factory coil. The SOS coils look identical to the factory coils, but there are more windings that are a heavier gauge wire in every SOS coil. The windings produce up to 40,000 volts at WOT, which is a 38 percent increase over the stock coils. More voltage equates to a more complete burn of the air/fuel, which should add to the overall performance.After testing with just the Performance Distributors coil packs (and gaining 10.2 hp over stock) we swapped over to the recommended Autolite plugs with the wider .065-inch gap. Make sure to blow the dust and debris out of the spark plug tubes first! The new Autolites were torqued to 13 ft-lbs.The SOS coils were slipped into the spark plug tubes and the fasteners torqued to 105 in-lbs. The electrical connectors were reattached to each coil. It sounded sharp when restarted, but better yet, there were no check engine lights or drivability concerns.The Charger was tested one more time with the Performance Distributors SOS coils, Autolite plugs, and wider gaps; and they didn’t let anyone down. The peak torque increased to 347 lb-ft at 4,250 rpm and the horsepower soared to 314 hp at 5,150 rpm. The average torque reading rose to 327 lb-ft, and the average horsepower increased to 289 hp.The dyno traces show the stock tune in red, and the SOS coils with Autolite plugs in green. The increase in peak numbers—11 for hp and 10 lb-ft for torque—are certainly nice, but take a look at the average improvement across the entire power band. This is real grunt you can feel in the seat of your pants!